151x Ccna 1 Ejw Ch 7 Answers
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CCNA 1 Chapter 7 Ethernet Technologies Ethernet and its associated IEEE 802.3 protocols are part of the world's most important networking standards. Because of the great success of the original Ethernet and the soundness of its design, it has evolved over time. This evolution was in response to the developing needs of modern LANs. It is likely that Ethernet will continue to evolve in response to future demands for network capability. In Chapter 6, "Ethernet Fundamentals," you were introduced to both the history of Ethernet and the standards associated with it. You also learned that the term Ethernet refers to a family of Ethernet technologies. This chapter discusses the Ethernet technologies in more detail.
Concept Questions Demonstrate your knowledge of these concepts by answering the following questions in the space provided. 1.
2.
One process that is particularly important at the physical layer level is the signal quality error (SQE) signal. This signal is typical of something we will see in many networking technologies. At the physical layer, the network is "alive" with communications other than our user data to ensure a properly functioning network. SQE is always used in half duplex; it is not required but is permitted in full-duplex operation. What are the reasons for SQE being active? • Whenever there is a collision on the medium •
Whenever there is an improper signal on the medium. Improper signals might include detected jabber, or the reflections that result from a cable fault such as a short. (There are separate conditions depending on which medium is attached.)
•
Whenever a transmission has been interrupted as jabber, that is, it has transmitted longer than allowed
•
Within 4 to 8 microseconds following a normal transmission, to indicate that the outbound frame was successfully transmitted
Describe the 5-4-3 rule. 10 Mbps Ethernet operates within the timing limits offered by a series of not more than five segments separated by no more than four repeaters. That is, no more than four repeaters may be connected in series between any two distant stations. The coaxial implementations have a further requirement that there be no more than three populated segments between any two distant stations. The other two allowed coaxial segments are used to extend the diameter of the collision domain
151x CCNA 1 EJW Ch 7 Answers
2
and are called link segments. The primary characteristic of a link segment is that it has exactly two devices attached. 3.
What are some reasons to use 100BASE-FX (introduced as part of the 802.3u-1995 standard) as opposed to other Ethernet standards? At the time copper-based Fast Ethernet was introduced, a fiber version was desired for backbone applications, connections between floors and buildings where copper is less desirable and high noise environments. 100BASE-FX was also positioned as an alternative to the then-popular FDDI (100 Mbps dual fiber optic token ring). However, the vast majority of Fast Ethernet installations today are 100BASE-TX. One reason for the relative lack of adoption of 100BASE-FX was the rapidity of the introduction of Gigabit Ethernet copper and fiber standards, which are now the dominant technology for backbone installations, high-speed cross-connects, and general infrastructure needs.
4.
Ethernet, Fiber Distributed Data Interface (FDDI), and Token Ring are widely used LAN technologies that account for virtually all deployed LANs. LAN standards specify cabling and signaling at the physical and data link layers of the OSI model. Because they are widely adhered to, this book covers the Ethernet and IEEE 802.3 LAN standards. Why do you suppose that Ethernet technology is so heavily used? Ethernet is well suited to applications in which a local communication medium must carry sporadic, occasionally heavy traffic at high-peak data rates. Ethernet was considered high-speed when it was first available.
5.
When it was developed, Ethernet was designed to fill the middle ground between long-distance, low-speed networks and specialized, computer-room networks carrying data at high speeds for limited distances. Ethernet is well suited to applications in which a local communication medium must carry sporadic, occasionally heavy traffic at high-peak data rates. Why is Ethernet so well suited to this kind of traffic? Ethernet was designed to fill the middle ground between long-distance, low-speed networks and specialized, computer-room networks carrying data at high speeds for very limited distances.
6.
Today, the term standard Ethernet refers to all networks using Ethernet (a shared-medium technology) that generally conform to Ethernet specifications, including IEEE 802.3. To use this shared-medium technology, Ethernet uses the carrier sense multiple access collision detect (CSMA/CD) protocol to allow the networking devices to negotiate for the right to transmit. What are the major benefits of Ethernet? It was designed to enable sharing resources on a local workgroup level. Design goals included simplicity, low cost, compatibility, fairness, low delay, and high speed.
151x CCNA 1 EJW Ch 7 Answers
3
Vocabulary Exercise Define the following terms as completely as you can. Use the online curriculum or CCNA 1 Chapter 7 from the Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised Third Edition, for help. 4D-PAM5[md]The symbol encoding method used in 1000BASE-T. The four dimensional quinary symbols (4D) received from the 8B1Q4 data encoding are transmitted using five voltage levels (PAM5). Four symbols are transmitted in parallel each symbol period. 8B1Q4[md]For IEEE802.3, the data encoding technique used by 1000BASE-T when converting GMII data (8B-8 bits) to four quinary symbols (Q4) that are transmitted during one clock (1Q4). 10BASE-2[md]A 10-Mbps baseband Ethernet specification that uses 50-ohm thin coaxial cable. 10BASE2, which is part of the IEEE 802.3 specification, has a distance limit of 185 meters per segment. 10BASE-5[md]A 10-Mbps baseband Ethernet specification that uses standard (thick) 50-ohm baseband coaxial cable. 10BASE5, which is part of the IEEE 802.3 baseband physical layer specification, has a distance limit of 500 meters per segment. 10BASE-T[md]A 10-Mbps baseband Ethernet specification that uses two pairs of Category 3, 4, or 5 twisted-pair cabling. One pair of wires is used to receive data and the other pair is used to transmit data. 10BASE-T, which is part of the IEEE 802.3 specification, has a distance limit of approximately 100 meters per segment. 100BASE-FX[md]A 100-Mbps baseband Fast Ethernet specification that uses two strands of multimode fiber-optic cable per link. To guarantee proper signal timing, a 100BASE-FX link cannot exceed 400 meters in length. 100BASE-TX[md] the predominant form of Fast Ethernet, providing 100 Mbit/s Ethernet. 100BASE-TX runs over two pairs of wires in category 5 cable. 1000BASE-LX[md] Long wavelength, single-mode optical fiber 1000BASE-SX[md]1000 Mbps multimode optical fiber that has a maximum physical distance of 220m. 1000BASE-T[md] 1000 Mbps Category 5 UTP that has a maximum physical distance of 100m.
151x CCNA 1 EJW Ch 7 Answers
4
Focus Questions 1.
What are the field names in a generic frame? Start Frame field, Address field, Length/Type field. Data field, and Frame Check Sequence (FCS) field
2.
What happens on an Ethernet network after a collision occurs? 2 bits attempt to propagate the same network at the same time. Stations on a CSMA/CD network listen for quiet, at which time it’s okay to transmit. However, if two stations transmit at the same time, a collision occurs and neither station’s transmission succeeds. All other stations on the network also hear the collision and wait for silence. The transmitting stations, in turn, each wait a random period of time (a backoff period) before retransmitting, thus minimizing the probability of a second collision. Editor’s Note: Answers may vary. It depends where the collision occurs on the Ethernet network.
3.
What address information is found in a layer 2 frame? Destination and Source MAC Address
4.
What are the features of Token Ring? In a Token Ring network, individual hosts are arranged in a ring. A special data token circulates around the ring. When a host wants to transmit, it seizes the token, transmits the data for a limited time, and then places the token back in the ring, where it can be passed along, or seized, by another host. Editor’s Note: “Token Ring” is covered on page 65 in CCNA 1 Chapter 2 in the CCNA 1 and 2 Companion Guide, Revised Third Edition.
5.
What are three advantages that optical fiber has over copper wiring? Fast Transmission speeds, less conducive to interference, longer cable lengths
6.
What network device must all network traffic pass through on a star topology? Hub or Switch
7.
What factors led to the widespread growth of Ethernet networks? The two main factors were advances in technology that made it not only affordable on a wide-scale but also increased the performance to a degree
151x CCNA 1 EJW Ch 7 Answers
5
that human efficiency could be greatly increased using Ethernet as a medium. Editor’s Note: Answers may vary. There are many factors that contribute to the widespread growth of Ethernet networks: increase in packets, changes in protocols, etc. 8.
What is the maximum distance for thick Ethernet without using a repeater? A. 185 m (606.95 feet) B. 250 m (820.2 feet) C. 500 m (1640.4 feet) D. 800 m (2624.64 feet)
9.
10 Mbps Ethernet operates within the timing limits offered by a series of not more than ________ segments separated by no more than ________ repeaters. A. Three, two B. Four, three C. Five, four D. Six, five
10.
Fast Ethernet supports up to what transfer rate? A. 5 Mbps B. 10 Mbps C. 100 Mbps D. 1000 Mbps
11.
Identify two Gigabit Ethernet cable specifications. A. 1000BASE-TX B. 1000BASE-FX C. 1000BASE-CS D. 1000BASE-LX E. 1000BASE-X
12.
What is the transmission medium for 1000BASE-SX? A. Long-wave laser over single-mode and multimode fiber B. Category 5 UTP copper wiring C. Balanced, shielded, 150 ohm, two-pair STP copper cable D. Short-wave laser over multimode fiber
13.
4D-PAM5 encoding is used in which of the following Gigabit Ethernet standards? A. 1000BASE-LX B. 1000BASE-SX C. 1000BASE-T D. 1000BASE-CX
151x CCNA 1 EJW Ch 7 Answers
6
14.
What is the IEEE standard for 10-Gigabit Ethernet? A. 802.3z B. 802.3u C. 802.3ae D. 803.3
151x CCNA 1 EJW Ch 7 Answers
CCNA 1 Chapter 7 Ethernet Technologies Ethernet and its associated IEEE 802.3 protocols are part of the world's most important networking standards. Because of the great success of the original Ethernet and the soundness of its design, it has evolved over time. This evolution was in response to the developing needs of modern LANs. It is likely that Ethernet will continue to evolve in response to future demands for network capability. In Chapter 6, "Ethernet Fundamentals," you were introduced to both the history of Ethernet and the standards associated with it. You also learned that the term Ethernet refers to a family of Ethernet technologies. This chapter discusses the Ethernet technologies in more detail.
Concept Questions Demonstrate your knowledge of these concepts by answering the following questions in the space provided. 1.
2.
One process that is particularly important at the physical layer level is the signal quality error (SQE) signal. This signal is typical of something we will see in many networking technologies. At the physical layer, the network is "alive" with communications other than our user data to ensure a properly functioning network. SQE is always used in half duplex; it is not required but is permitted in full-duplex operation. What are the reasons for SQE being active? • Whenever there is a collision on the medium •
Whenever there is an improper signal on the medium. Improper signals might include detected jabber, or the reflections that result from a cable fault such as a short. (There are separate conditions depending on which medium is attached.)
•
Whenever a transmission has been interrupted as jabber, that is, it has transmitted longer than allowed
•
Within 4 to 8 microseconds following a normal transmission, to indicate that the outbound frame was successfully transmitted
Describe the 5-4-3 rule. 10 Mbps Ethernet operates within the timing limits offered by a series of not more than five segments separated by no more than four repeaters. That is, no more than four repeaters may be connected in series between any two distant stations. The coaxial implementations have a further requirement that there be no more than three populated segments between any two distant stations. The other two allowed coaxial segments are used to extend the diameter of the collision domain
151x CCNA 1 EJW Ch 7 Answers
2
and are called link segments. The primary characteristic of a link segment is that it has exactly two devices attached. 3.
What are some reasons to use 100BASE-FX (introduced as part of the 802.3u-1995 standard) as opposed to other Ethernet standards? At the time copper-based Fast Ethernet was introduced, a fiber version was desired for backbone applications, connections between floors and buildings where copper is less desirable and high noise environments. 100BASE-FX was also positioned as an alternative to the then-popular FDDI (100 Mbps dual fiber optic token ring). However, the vast majority of Fast Ethernet installations today are 100BASE-TX. One reason for the relative lack of adoption of 100BASE-FX was the rapidity of the introduction of Gigabit Ethernet copper and fiber standards, which are now the dominant technology for backbone installations, high-speed cross-connects, and general infrastructure needs.
4.
Ethernet, Fiber Distributed Data Interface (FDDI), and Token Ring are widely used LAN technologies that account for virtually all deployed LANs. LAN standards specify cabling and signaling at the physical and data link layers of the OSI model. Because they are widely adhered to, this book covers the Ethernet and IEEE 802.3 LAN standards. Why do you suppose that Ethernet technology is so heavily used? Ethernet is well suited to applications in which a local communication medium must carry sporadic, occasionally heavy traffic at high-peak data rates. Ethernet was considered high-speed when it was first available.
5.
When it was developed, Ethernet was designed to fill the middle ground between long-distance, low-speed networks and specialized, computer-room networks carrying data at high speeds for limited distances. Ethernet is well suited to applications in which a local communication medium must carry sporadic, occasionally heavy traffic at high-peak data rates. Why is Ethernet so well suited to this kind of traffic? Ethernet was designed to fill the middle ground between long-distance, low-speed networks and specialized, computer-room networks carrying data at high speeds for very limited distances.
6.
Today, the term standard Ethernet refers to all networks using Ethernet (a shared-medium technology) that generally conform to Ethernet specifications, including IEEE 802.3. To use this shared-medium technology, Ethernet uses the carrier sense multiple access collision detect (CSMA/CD) protocol to allow the networking devices to negotiate for the right to transmit. What are the major benefits of Ethernet? It was designed to enable sharing resources on a local workgroup level. Design goals included simplicity, low cost, compatibility, fairness, low delay, and high speed.
151x CCNA 1 EJW Ch 7 Answers
3
Vocabulary Exercise Define the following terms as completely as you can. Use the online curriculum or CCNA 1 Chapter 7 from the Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised Third Edition, for help. 4D-PAM5[md]The symbol encoding method used in 1000BASE-T. The four dimensional quinary symbols (4D) received from the 8B1Q4 data encoding are transmitted using five voltage levels (PAM5). Four symbols are transmitted in parallel each symbol period. 8B1Q4[md]For IEEE802.3, the data encoding technique used by 1000BASE-T when converting GMII data (8B-8 bits) to four quinary symbols (Q4) that are transmitted during one clock (1Q4). 10BASE-2[md]A 10-Mbps baseband Ethernet specification that uses 50-ohm thin coaxial cable. 10BASE2, which is part of the IEEE 802.3 specification, has a distance limit of 185 meters per segment. 10BASE-5[md]A 10-Mbps baseband Ethernet specification that uses standard (thick) 50-ohm baseband coaxial cable. 10BASE5, which is part of the IEEE 802.3 baseband physical layer specification, has a distance limit of 500 meters per segment. 10BASE-T[md]A 10-Mbps baseband Ethernet specification that uses two pairs of Category 3, 4, or 5 twisted-pair cabling. One pair of wires is used to receive data and the other pair is used to transmit data. 10BASE-T, which is part of the IEEE 802.3 specification, has a distance limit of approximately 100 meters per segment. 100BASE-FX[md]A 100-Mbps baseband Fast Ethernet specification that uses two strands of multimode fiber-optic cable per link. To guarantee proper signal timing, a 100BASE-FX link cannot exceed 400 meters in length. 100BASE-TX[md] the predominant form of Fast Ethernet, providing 100 Mbit/s Ethernet. 100BASE-TX runs over two pairs of wires in category 5 cable. 1000BASE-LX[md] Long wavelength, single-mode optical fiber 1000BASE-SX[md]1000 Mbps multimode optical fiber that has a maximum physical distance of 220m. 1000BASE-T[md] 1000 Mbps Category 5 UTP that has a maximum physical distance of 100m.
151x CCNA 1 EJW Ch 7 Answers
4
Focus Questions 1.
What are the field names in a generic frame? Start Frame field, Address field, Length/Type field. Data field, and Frame Check Sequence (FCS) field
2.
What happens on an Ethernet network after a collision occurs? 2 bits attempt to propagate the same network at the same time. Stations on a CSMA/CD network listen for quiet, at which time it’s okay to transmit. However, if two stations transmit at the same time, a collision occurs and neither station’s transmission succeeds. All other stations on the network also hear the collision and wait for silence. The transmitting stations, in turn, each wait a random period of time (a backoff period) before retransmitting, thus minimizing the probability of a second collision. Editor’s Note: Answers may vary. It depends where the collision occurs on the Ethernet network.
3.
What address information is found in a layer 2 frame? Destination and Source MAC Address
4.
What are the features of Token Ring? In a Token Ring network, individual hosts are arranged in a ring. A special data token circulates around the ring. When a host wants to transmit, it seizes the token, transmits the data for a limited time, and then places the token back in the ring, where it can be passed along, or seized, by another host. Editor’s Note: “Token Ring” is covered on page 65 in CCNA 1 Chapter 2 in the CCNA 1 and 2 Companion Guide, Revised Third Edition.
5.
What are three advantages that optical fiber has over copper wiring? Fast Transmission speeds, less conducive to interference, longer cable lengths
6.
What network device must all network traffic pass through on a star topology? Hub or Switch
7.
What factors led to the widespread growth of Ethernet networks? The two main factors were advances in technology that made it not only affordable on a wide-scale but also increased the performance to a degree
151x CCNA 1 EJW Ch 7 Answers
5
that human efficiency could be greatly increased using Ethernet as a medium. Editor’s Note: Answers may vary. There are many factors that contribute to the widespread growth of Ethernet networks: increase in packets, changes in protocols, etc. 8.
What is the maximum distance for thick Ethernet without using a repeater? A. 185 m (606.95 feet) B. 250 m (820.2 feet) C. 500 m (1640.4 feet) D. 800 m (2624.64 feet)
9.
10 Mbps Ethernet operates within the timing limits offered by a series of not more than ________ segments separated by no more than ________ repeaters. A. Three, two B. Four, three C. Five, four D. Six, five
10.
Fast Ethernet supports up to what transfer rate? A. 5 Mbps B. 10 Mbps C. 100 Mbps D. 1000 Mbps
11.
Identify two Gigabit Ethernet cable specifications. A. 1000BASE-TX B. 1000BASE-FX C. 1000BASE-CS D. 1000BASE-LX E. 1000BASE-X
12.
What is the transmission medium for 1000BASE-SX? A. Long-wave laser over single-mode and multimode fiber B. Category 5 UTP copper wiring C. Balanced, shielded, 150 ohm, two-pair STP copper cable D. Short-wave laser over multimode fiber
13.
4D-PAM5 encoding is used in which of the following Gigabit Ethernet standards? A. 1000BASE-LX B. 1000BASE-SX C. 1000BASE-T D. 1000BASE-CX
151x CCNA 1 EJW Ch 7 Answers
6
14.
What is the IEEE standard for 10-Gigabit Ethernet? A. 802.3z B. 802.3u C. 802.3ae D. 803.3
151x CCNA 1 EJW Ch 7 Answers
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